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Fire extinguisher

A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not designed for use on an out-of-control fire, such as one which has reached the ceiling, endangers the user (i.e. no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire department. Typically, a fire extinguisher consists of a handheld cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire.

There are two main types of fire extinguishers: Stored pressure and generated pressure. In stored pressure units, the expellant is stored in the same chamber as the firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam are pressurized with air. Stored pressure are the most common types of fire extinguishers. Cartridge-operated extinguishers, contain the expellant gas in a separate cartridge that is punctured prior to discharge, exposing the propellant to the agent. These types as are not as common, used primarily in areas such as industrial facilities, where they receive higher-than-average use. They have the advantage of simple and prompt recharge, allowing an operator to discharge the extinguisher, recharge it, and return to the fire in an reasonable amount of time. Unlike stored pressure types, these extinguishers utilize compressed carbon dioxide instead of nitrogen, although nitrogen cartridges are used on low temperature (-60 rated) models. Cartridge operated types are available in dry chemical and dry powder in the US and water, wetting agent, foam, and dry powder(ABC, BC, or D) in the rest of the world.

Fire extinguishers are further divided into handheld and cart-mounted, also called wheeled extinguishers. Handheld extinguishers weight from 2 to 30 pounds (1 to 14 kilograms), and are hence easily portable by hand. They exist in both stored- and generated-pressure types and contain all types of suppressants. Cart-mounted units typically weigh 50+ pounds (23+ kilograms), are cartridge-operated, and typically contain either dry chemical, Purple-K, foam, Halon, Halotron-1 or CO2. Wheeled models are most commonly found at construction sites, airportrunways, heliports, and temporary landing sites.

History

The first automatic fire extinguisher of which there is any record was patented in England in 1723 by Ambrose Godfrey, a celebrated chemist. It consisted of a cask of fire-extinguishing liquid containing a pewter chamber of gunpowder. This was connected with a system of fuses which were ignited, exploding the gunpowder and scattering the solution. This device was probably used to a limited extent, as Bradley's Weekly Messenger for November 7, 1729, refers to its efficiency in stopping a fire in London.

A vial was suspended in the cylinder containing concentrated sulfuric acid. Depending on the type of extinguisher, the vial of acid could be broken in one of two ways. One used a plunger to break the acid vial, while the second released a lead bung that held the vial closed. Once the acid was mixed with the bicarbonate solution, carbon dioxide gas was expelled and thereby pressurize the water. The pressurized water was forced from the canister through a nozzle or short length of hose.

The cartridge-operated extinguisher was invented by Read & Campbell of England in 1881, which used water or water-based solutions. They later invented a carbon tetrachloride model called the "Petrolex" which was marketed toward automotive use.

The chemical foam extinguisher was invented around 1905 by Alexander Laurant of Russia, who first used it to extinguish a pan of burning naptha. It works and looks similar to the soda-acid type, but the inner parts are different. The main tank contains a solution of water, foam compound (usually made from licorice root) and sodium bicarbonate. A cylindrical metal or plastic chamber holds about a quart and a half of 13% aluminum sulfate and is capped with a lead cap. When the unit is turned over, the chemicals mix, producing CO2 gas. The licorice causes some of the CO2 bubbles to become trapped in the liquid and is discharged on the fire as a thick whitish-brown foam.

Around 1912 Pyrene invented the carbon tetrachloride (CTC) extinguisher, which expelled the liquid from a brass or chrome container by a handpump; it was usually of 1 imperial quart (1.1 L) or 1 imperial pint (0.6 L) capacity but was also available in up to 2 imperial gallon (9 L) size. A further variety consisted of a glass bottle "bomb" filled with the liquid that was intended to be hurled at the base of a fire. The CTC vaporized and extinguished the flames by creating a dense, oxygen-excluding blanket of fumes, and to a lesser extent, inhibiting the chemical reaction. The extinguisher was suitable for liquid and electrical fires, and was popular in motor vehicles for the next 60 years. In the 1940s, Germany invented the liquid chlorobromomethane (CBM) for use in aircraft. It was more effective and slightly less toxic than carbon tetrachloride and was used until 1969. Methyl Bromide was discovered as an extinguishing agent in the 1920s and was used extensively in Europe. It is a low-pressure gas that works by inhibiting the chain reaction of the fire and is the most toxic of the vaporizing liquids, used until the 1960s. The vapor and combustion by-products of all vaporizing liquids were highly toxic, and could cause death in confined spaces.

The carbon dioxide (CO2) extinguisher was invented (at least in the US) by the Walter Kidde Company in 1924 in response to Bell Telephone's request for an electrically non-conductive chemical to extinguisher the previously difficult to extinguish fires in telephone switchboards. It consisted of a tall metal cylinder containing 7.5 lbs. of CO2 with a wheel valve and a woven brass, cotton covered hose, with a composite funnel-like horn as a nozzle. CO2 is still popular today as it is a ozone-friendly clean agent and is useful for a extinguishing a person who is on fire, hence its widespread use in film and television.

In 1928, DuGas (later bought by Ansul) came out with a cartridge-operated dry chemical extinguisher, which used sodium bicarbonate specially treated with chemicals to render it free-flowing and moisture-resistant. It consisted of a copper cylinder with an internal CO2 cartridge. The operator turned a wheel valve on top to puncture the cartridge and squeezed a lever on the valve at the end of the hose to discharge the chemical. This was the first agent available for large scale three-dimensional liquid and pressurized gas fires, and was but remained largely a specialty type until the 1950s, when small dry chemical units were marketed for home use. ABC dry chemical came over from Europe in the 1950s, with Super-K being invented in the early 60s and Purple-K being developed by the US Navy in the late 1960s.

Halon 1211 came over to the US in the 1970s, and had been used there since the late 40s or early 50s. Halon 1301 had been developed by DuPont and the US Army in 1954. Both work by inhibiting the chain reaction of the fire, and in the case of Halon 1211, cooling class A fuels as well. Halon is still in use today, but is falling out of favor for many uses due to its environmental impact. Europe and Australia have severly restricted its use, but it is still widely available in North America, the Middle East, and Asia.

Classification

Internationally there are several accepted classification methods for hand-held fire extinguishers. Each classification is useful in fighting fires with a particular group of fuel.

Australia

Type

Pre-1997

Current

Class

Water

Solid red

A

Foam

Solid blue

Red with a blue band

A

B

Dry chemical (powder)

Red with a white band

A

B

C

E

Carbon dioxide

Red with a black band

A (limited)

B

C

E

F

Vapourising liquid (not halon)

Red with a yellow band

A

B

C

E

Halon

Solid yellow

—

A

B

E

Wet chemical

Solid oatmeal

Red with an oatmeal band

A

F

In Australia, yellow (Halon) fire extinguishers are illegal to own or use on a fire, unless an essential use exemption has been granted.

United Kingdom

According to the standard BS EN 3, fire extinguishers in the United Kingdom as all throughout Europe are red RAL 3000, and a band or circle of a second color covering at least 5% of the surface area of the extinguisher indicates the contents. Before 1997, the entire body of the fire extinguisher was color coded according to the type of extinguishing agent.

Type

Old Code

BS EN 3 Colour Code

Fire Class

Water

Signal Red

Signal Red

A

Foam

Cream

Red with a Cream panel above the operating instructions

A

B

sometimes E

Dry powder

French Blue

Red with a Blue panel above the operating instructions

A

B

sometimes C

E

Carbon dioxide CO2

Black

Red with a Black panel above the operating instructions

B

E

Wet chemical

No F Class

Red with a Canary Yellow panel above the operating instructions

A

F

Class D powder

French Blue

Red with a Blue panel above the operating instructions

D

The UK recognizes six fire classes. Class A fires involve organic solids such as paper and wood. Class B fires involve flammable liquids. Class C fires involve flammable gases. Class D fires involve metals, Class E fires involve live electrical items and Class F fires involve cooking fat and oil.
Fire extinguishing capacity is rated by fire class using numbers and letters such as 13A, 55B.
EN 3 does not recognize a separate E class - this is an additional feature requiring special testing (dielectric test per EN 3-7:2004) and NOT passing this test makes it compulsory to add a special label (pictogram) indicating the inability to isolate the user from a live electric source.

In the UK the use of Halon gas is now illegal except under certain situations.

United States

There is no official standard in the United States for the color of fire extinguishers, though they are typically red, except for Class D extinguishers, which are usually yellow, and water, which usually silver, or white if water mist. Extinguishers are marked with pictograms depicting the types of fires that the extinguisher is approved to fight. In the past, extinguishers were marked with colored geometric symbols, and some extinguishers still use both symbols. The types of fires and additional standards are described in NFPA 10: Standard for Portable Fire Extinguishers, 2007 edition.

The Underwriters Laboratories rate fire extinguishing capacity in accordance with UL/ANSI 711: Rating and Fire Testing of Fire Extinguishers. The ratings are described using numbers preceding the class letter, such as 1-A:10-B:C. The number preceding the A multiplied by 1.25 gives the equivalent extinguishing capability in gallons of water. The number preceding the B indicates the size of fire in square feet that an ordinary user should be able to extinguish. There is no additional rating for class C, as it only indicates that the extinguishing agent will not conduct electricity, and an extinguisher will never have a rating of just C.

Installation

Fire extinguishers are typically fitted in buildings at an easily-accessible location, such as against a wall in a high-traffic area. They are also often fitted to motor vehicles, watercraft, and aircraft - this is required by law in many jurisdictions, for identified classes of vehicles. Under NFPA 10 all commercial vehicles must carry at least one fire extinguisher (size/UL rating depending on type of vehicle and cargo (ie. fuel tankers typically must have a 9.1 kg (20 lb). when most others can carry a 2.3 kg (5 lb).) The revised NFPA 10 created criteria on the placement of "Fast Flow Extinguishers" in locations such as those storing and transporting pressurized flammable liquids and pressurized flammable gas or areas with possibility of three dimensional class B hazards are required to have "fast flow" extinguishers as required by NFPA 5.5.1.1.
Varying classes of competition vehicles require fire extinguishing systems, the simplest requirements being a 1A10BC handheld portable extinguisher mounted to the interior of the vehicle.

Types of extinguishing agents

Dry chemical

Powder based agent that extinguishes by separating the four parts of the fire tetrahedron. It prevents the chemical reaction between heat, fuel and oxygen and halts the production of fire sustaining "free-radicals", thus extinguishing the fire.

Monoammonium phosphate, also known as ABC Dry Chemical, used on class A, B, and C fires. It receives its class A rating from the agents ability to melt and flow at 177 °C (350 °F) to smother the fire. More corrosive than other dry chemical agents. Yellow in color.

Sodium bicarbonate, "regular" or "ordinary" used on class B and C fires, was the first of the dry chemical agents developed. It interrupts the fire's chemical reaction, and was very common in commercial kitchens before the advent of wet chemical agents, but now is falling out of favor, as it is much less effective than wet chemical agents for class K fires, less effective than Purple-K for class B fires, and is ineffective on class A fires. White or Blue in color.

Potassium bicarbonate (aka Purple-K), used on class B and C fires. About two times as effective on class B fires as sodium bicarbonate. The preferred dry chemical agent of the oil and gas industry. The only dry chemical agent certified for use in AR-FF by the NFPA. Violet in color.

Potassium bicarbonate & Urea Complex (aka Monnex), used on Class B and C fires. More effective than all other powders due to its ability to decrepitate (where the powder breaks up into smaller particles) in the flame zone creating a larger surface area for free radical inhibition.

Potassium Chloride, or Super-K dry chemical was developed in an effort to create a high efficiency, protein-foam compatible dry chemical. Developed in the 60s, prior to Purple-K, it was never as popular as other agents since being a salt, it was quite corrosive. For B and C fires, white in color.

Foam-Compatible, which is a sodium bicarbonate (BC) based dry chemical, was developed for use with protein foams for fighting class B fires. Most dry chemicals contain metal stearates to waterproof them, but these will tend to destroy the foam blanket created by protein (animal) based foams. Foam compatible type uses silicone as a waterproofing agent, which does not harm foam. Effectiveness is identical to regular dry chemical, and it is light green in color (some Ansul brand formulations are blue). This agent is generally no longer used since most modern dry chemicals are considered compatible with sythetic foams such as AFFF.

MET-L-KYL is a specialty variation of sodium bicarbonate for fighting pyrophoric liquid fires (ignite on contact with air). In addition to sodium bicarbonate, it also contains silica gel particles. The sodium bicarb interrupts the chain reaction of the fuel and the silica soaks up any unburned fuel, preventing contact with air. It is effective on other class B fuels as well. Blue in color.

Foams

Applied to fuel fires as either an aspirated (mixed & expanded with air in a branch pipe) or non aspirated form to form a frothy blanket or seal over the fuel, preventing oxygen reaching it. Unlike powder, foam can be used to progressively extinguish fires without flashback.

AFFF (aqueous film forming foam), used on A and B fires and for vapor suppression. The most common type in portable extinguishers. It contains flouro tensides which can be accumulated in human body. The long-term effects of this on the human body and environment are unclear at this time.

AR-AFFF (Alcohol-resistant aqueous film forming foams), used on fuel fires containing alcohol. Forms a membrane between the fuel and the foam preventing the alcohol from breaking down the foam blanket.

FFFP (film forming fluoroprotein) contains naturally occurring proteins from animal by-products and synthetic film-forming agents to create a foam blanket that is more heat resistant then the strictly synthetic AFFF foams. FFFP works well on alcohol-based liquids and is used widely in motorsports.

Water

Cools burning material.

APW (Air pressurized water) cools burning material by absorbing heat from burning material. Effective on Class A fires, it has the advantage of being inexpensive, harmless, and relatively easy to clean up. In the United States, APW units contain 2.5 gallons of water in a tall, chrome-plated cylinder. In Europe, they are typically red, containing 6-9 liters (1.75-2.5 gallons) of water.

Water Mist uses a fine misting nozzle to break up a stream of deionized water to the point of not conducting electricity back to the operator. Class A and C rated. It is used widely in hospitals for the reason that, unlike other clean-agent suppressants, it is harmless and non-contaminant. These extinguishers come in 1.75 and 2.5 gallon units, painted white in the United States and red in Europe.

Wet chemical and water additives

Wet Chemical (potassium acetate, carbonate, or citrate) extinguishes the fire by forming a soapy foam blanket over the burning oil (saponification) and by cooling the oil below its ignition temperature. Generally class A and K (F in Europe) only, although newer models are outfitted with misting nozzles as those used on water mist units to give these extinguishers class B and C firefighting capability.

Wetting Agents Detergent based additives used to break the surface tension of water and improve penetration of Class A fires.

Antifreeze Chemicals added to water to lower its freezing point to about -40 degrees Fahrenheit. Has no appreciable effect on extinguishing performance.

Clean agents and carbon dioxide

Agent displaces oxygen (CO2 or inert gases), removes heat from the combustion zone (Halotron, FE-36) or inhibits chemical chain reaction (Halons). They are labeled clean agents because they do not leave any residue after discharge which is ideal for sensitive electronics and documents.

Halon (including Halon 1211 and Halon 1301), a gaseous agent that inhibits the chemical reaction of the fire. Classes B:C for lower weight fire extinguishers (2.3 kg ; under 9 lbs) and A:B:C for heavier weights (4.1-7.7 kg ; 9-17 lbs). Banned from new production, except for military use, as of January 1, 1994 as its properties contribute to ozone depletion and long atmospheric lifetime, usually 400 years. Halon was completely banned in Europe resulting in stockpiles being sent to the United States for reuse. Although production has been banned, the reuse is still permitted. Halon 1301 and 1211 are being replaced with new halons which have no ozone depletion properties and low atmospheric lifetimes, but are less effective. Currently Halotron I, Halotron II, FE-36 Cleanguard and FM-200 are meant to be replacements with significantly reduced ozone depletion potential.

CO2, a clean gaseous agent which displaces oxygen. Highest rating for 7.7 kg (20 pound) portable CO2 extinguishers is 10B:C. Not intended for Class A fires. CO2 is not suitable for use on fires containing their own oxygen source, metals, or cooking media, however, it is one on the best agents to use on a person who is on fire.

Class D

There are several Class D fire extinguisher agents available, some will handle multiple types of metals, others will not. All U.S. types are rated Class D only.

Sodium Chloride (Super-D, Met-L-X or METAL.FIRE.XTNGSHR)-contains sodium chloride salt and thermoplastic additive. Plastic melts to form a oxygen-excluding crust over the metal, and the salt dissipates heat. Useful on most metals, magnesium, titanium, aluminum, sodium, potassium, and zirconium.

Graphite based (G-Plus, G-1, Lith-X, Pyromet or METAL.FIRE.XTNGSHR)-contains dry graphite that smothers burning metals. First type developed, designed for magnesium, works on other metals as well.

Copper based (Copper Powder Navy125S)-developed by the U.S. Navy in the 70s for hard to control lithium fires. Powder smothers and acts as a heat sink to dissipate heat, but also forms a copper-lithium alloy on the surface which is non-combustible and cuts off the oxygen supply. Will cling to a vertical surface-lithium only.

Sodium carbonate based (Na-X)-used where stainless steel piping and equipment could be damaged by sodium chloride based agents to control sodium, potassium, and sodium-potassium alloy fires. Limited use on other metals. Smothers and forms a crust.

Most Class D extinguishers will have a special low velocity nozzle or discharge wand to gently apply the agent in large volumes to avoid disrupting any finely divided burning materials. Agents are also available in bulk and can be applied with a scoop or shovel.

Maintenance

Most countries in the world require regular fire extinguisher maintenance by a competent person to operate safely and effectively, as part of fire safety legislation. Lack of maintenance can lead to an extinguisher not discharging when required, or rupturing when pressurized. Deaths have occurred, even in recent times, from corroded extinguishers exploding.

There is no all-encompassing fire code in the United States. Generally, most municipalities (by adoption of the International Fire Code) require inspections every 30 days to ensure the unit is pressurized and unobstructed (done by an employee of the facility) and an annual inspection by a qualified technician. Hydrostatic pressure testing for all types of extinguishers is also required, generally every five years for water and CO2 models up to every 12 years for dry chemical models.

Recently the National Fire Protection Association and ICC voted to allow for the elimination of the 30 day inspection requirement so long as the fire extinguisher is monitored electronically. According to NFPA, the system must provide record keeping in the form of an electronic event log at the control panel. The system must also constantly monitor an extinguisher’s physical presence, internal pressure and whether an obstruction exists that could prevent ready access. In the event that any of the above conditions are found, the system must send an alert to officials so they can immediately rectify the situation. Electronic monitoring can be wired or wireless.

In the UK, three types of maintenance are required:

Basic Service: All types of extinguisher require a basic inspection annually to check weight, correct pressure (using a special tool, not just looking at the gauge) and for signs of damage or corrosion, cartridge extinguishers are opened up for internal inspection & check weighing of the cartridge, labels are checked for legibility, where possible dip tubes, hoses and mechanisms checked for clear free operation.

Extended Service: Water, Wet Chemical, Foam & Powder extinguishers require every five years a more detailed examination including a test discharge of the extinguisher and recharging- on stored pressure extinguishers this is the only opportunity to internally inspect for damage/corrosion. By recharging fresh agent is used as they all have a shelf life, even water goes foul inside an extinguisher; Note: extinguishers should be percentage tested according to total number of units in any given area. Some extinguishers contain pressure in excess of 1.38 MPa (200psi) and this internal pressure over periods of time affects each brand & make differently depending on their placement & location.

Overhaul: CO2 extinguishers, due to their high operating pressure, are subject to pressure vessel safety legislation and must be hydraulic pressure tested, inspected internally & externally and date stamped every 10 years. As it cannot be pressure tested a new valve is also fitted. If replacing any part of the extinguisher (valve, horn etc) with a part from another manufacturer then the extinguisher will lose its fire rating. This may invalidate insurance, as would incorrect or inadequate servicing if it were to be found.

In the United States there are 3 types of service as well:

Maintenance Inspection: All types, annually (with the exception of water types which require a yearly recharge), consists of a physical maintenance and visual inpection. The extinguisher is checked to make sure it has good pressure (gauge in green or proper cartridge weight), has the correct volume of agent (tech weighs it), is within the required hydrotest and internal maintenance intervals, is in good condition and all external parts are serviceable. Dry chemical and dry powder types are hit on the bottom with a rubber mallet to make sure the powder is free-flowing, which is called "fluffing" the powder. The tech will then attach a new tamper seal around the pin and a yearly service tag.

The extinguisher is emptied of its chemical and presure to check for proper operation. All components are disassembled, inspected, cleaned, lubed, or replaced if defective. Liquid agents are replaced at this time, dry agents may be re-used in in good condition, halon is recovered and re-used, but CO2 is simply discharged to the atmosphere. Extinguisher is then re-filled and recharged, after a "verification of service" collar is placed around the cylinder neck. It is impossible to properly install or remove a collar without depressurizing the extinguisher, although '''many fly-by-night companies either cut and tape these, cut and dab a little crazy-glue on the bottom of the cut area on the collar or put the largest one possible on so that it slips over the valve-watch out!!
Note: Cartridge-operated extinguishers should be visually examined, but do not require a verification of service collar.

Note: these are the required intervals for normal service conditions, if the extinguisher has been exposed to excessive heat, vibration, or mechanical damage it may need to be tested sooner.

The agent is emptied and depressurized and the valve is removed. After a thorough internal and external visual inspection, the cylinder is filled with water, placed inside a safety cage, and pressurized to the specified test pressure (varies with the type, age, and cylinder material) for the specified time period. If no failure, bulges, or leaks are detected, the cylinder passes. The cylinder is then emptied of water and thoroughly dried. CO2 types have the test date, company's ID, etc. stamped on the cylinder, all other types get a sticker on the back of the cylinder. Once dry, the units are recharged. Unlike the UK, the US does not rebuild extinguishers and replace valves at specific intervals unless parts are found to be defective, with the exception of halon. Halon types are often given new o-rings and valve stems at every internal maintenenace to minimize any leakage potential.

OEM equipment must be used for replacement parts for the extinguisher to maintain its UL rating. If parts are unavailable, replacement is recommended, keep in mind extinguishers have a projected service life of about 25-35 years, although many are of such quality that they can outlast this, but realize that science is ever-changing, and something that was the best available 30 years ago may not be acceptable for modern fire protection needs.

Fire extinguisher signs

Fire extinguisher identification signs are small signs designed to be mounted near a fire extinguisher, in order to draw attention to the extinguisher's location (Ex. If the Extinguisher is on a large pole the sign would generally be at the top of the pole so it can be seen from a distance) Such signs may be manufactured from a variety of materials, commonly self-adhesive vinyl, rigid PVC and aluminum.

In addition to words and pictographs indicating the presence of a fire extinguisher , some modern extinguisher ID signs also describe the extinguishing agent in the unit, and summarize the types of fire on which it may safely be used.

Some public and government buildings are often required, by local legal codes, to provide an ID sign for each extinguisher on the site.

Placement of fire extinguisher signs

Fire extinguisher signs are mounted above or to the side of the extinguisher they relate to.

Most licensing authorities have regulations describing the standard appearance of these signs (e.g. text height, pictographs used and so on).

Photo-luminescent fire extinguisher signs

Photo-luminescent fire extinguisher signs are made of a polymer that absorbs ambient light and releases it slowly in dark conditions - the sign "glows in the dark". Such signs are independent of an external power supply, and so offer a low-cost, reliable means of indicating the position of emergency equipment in dark or smoky conditions.

Photo-luminescent signs are sometimes mis-described as being reflective. A reflective material will only return ambient light for as long as the light source is supplied, rather than storing energy and releasing it over a period of time. However, many fire extinguishers and extinguisher mounting posts have strips of reflective adhesive tape placed on them to facilitate their location in situations where only emergency lighting or flashlights are available.

Older luminescent signs sometimes used a radioactive tritium source to energise the polymeric material. This source could pose a hazard when such signs are dismantled or damaged. Modern photoluminescent materials are, however, not radioactive.